US Submission to Meeting
of OECD Working Party on Existing Chemicals
February, 1999

The original version of the paper which
appears below was developed by the US EPA for presentation at a meeting
organized by the Center for Alternatives to Animal Testing (CAAT) at Johns
Hopkins University on January 26-27, 1999. The purpose of the CAAT meeting
was to identify alternatives to animal testing that could be applied to
Screening Information Data Set (SIDS) testing. Emphasis was placed upon
methods that are available now or are ready for validation. The current
paper extends the material that was presented at the CAAT meeting and reflects
EPA's perspectives on animal welfare issues and approaches in the context
of the HPV Challenge Program. This paper was further presented for consideration
by the Working Party on Existing Chemicals of the Organization for Economic
Cooperation and Development (OECD) on February 16-17, 1999. The paper proposes
approaches which could be used as part of an effort to minimize and optimize
animal usage when obtaining SIDS testing program data on High Production
Volume (HPV) chemicals, while still generating needed high quality information.
Opportunities include various reduction, refinement and replacement testing
strategies, as well as the employment of existing chemical testing data,
structure-activity relationships and the use of chemical categories to reduce
the need for testing. These proposals could be used for testing under both
the US HPV Challenge Program and the OECD's HPV Program.

EPA is mounting a very extensive program to obtain toxicological screening
information on chemicals of High Production Volume (HPV), that is, substances
produced in excess of 1M lb/year. Current information indicates that there
are about 2800 chemicals with that designation. Various parties have noted
that if each chemical in the program were to be tested for each of the
human health effects tests, a large number of animals would be employed.
In recognition of these concerns, the Agency has given thought to the
issue and is developing a strategy to reduce animal use while still generating
needed high quality health information.

Many different paths are being investigated to ensure the minimization
of animal usage and optimization of procedures for those animals that
go into test in the HPV testing program:

1. Decreasing chemicals going into test

a. Industry will determine whether adequate information on chemicals
already exists for the various endpoints. We do not want to retest chemicals.

b. EPA has released a data adequacy document which provides guidance
on making such determinations. EPA is also in the process of developing
guidance on procedures for searching the literature on other sources
of existing information.

c. Both the OECDs HPV Program and the HPV Challenge in the U.S.
encourage industry to develop categories of chemicals which can be assessed
as a group. These categories of related chemicals are expected to share
chemical and biological attributes. Instead of gaining information on
all members of a category, attempts will be made to identify testing
strategies that will identify individual materials which are representative
of the category. By testing the identified individual materials, we
should be able to characterize the potential fate and effects of the
whole category.

d. Structure-activity relationships (SAR) will help to identify potential
toxicities and other effects of individual chemicals based on Quantitative
Structure Activity Relationships (QSARs) or read-across
(i.e., analogue) approaches.

2. Minimizing and optimizing animal use in tests

The HPV testing program includes acquisition of health effects data
for chemicals on acute toxicity, reproductive toxicity, developmental
toxicity, 28-day repeated dose toxicity and mutagenicity. Mutagenicity
data requirements can be fulfilled with bacterial gene mutation, in vitro
mammalian cytogenetics (for pre-existing information) and in vivo micronucleus
(for pre-existing or newly generated information). Several opportunities
are available to evaluate the role of animals in testing and ensure that
their use is being appropriately addressed.

a. Replacement of animal testing. In some cases we need not
obtain health hazard information in animals. Mutagenicity testing can
be fulfilled by bacterial systems (e.g., Salmonella gene mutation) and,
in some cases, by cytogenetics in cultured mammalian cells.

b. Refinement of animal testing. EPA supports the employment
of federal and voluntary measures to ensure humane care and upkeep of
laboratory animals. In addition, we plan to utilize principles developed
in an upcoming document on humane endpoints from OECD. This report will
lay out signs of pain and stress in animals that should be utilized
in deciding when to terminate animals in test.

c. Reduction of animal testing. There are several opportunities
to reduce the number of animals committed to test. Table
1 illustrates potential animal savings for the case where some
or all health effects tests are performed on a chemical.

(1) Acute toxicity. There are 4 acute oral toxicity tests
approved by OECD. In the use of the traditional test (OECD 401), about
30 animals are employed to screen for toxicity following a single
exposure. Three alternative methods either refine or reduce animal
usage. Data from any of the acute methods may yield appropriate information
for HPV testing. Among the three alternative methods, EPA has identified
a preference for the up-and-down method (OECD 425) for the following
reasons: it greatly reduces the number of animals in comparison to
OECD 401 (the up-and-down method uses approximately 8 animals versus
30 in OECD 401); it gives a point estimate of the LD50; and it yields
information that can be used to estimate the toxicity of chemical
mixtures in accordance with the UN transport classification system.

(2) Reproductive and developmental toxicity. There are separate
test guidelines for 1-generation reproduction toxicity (OECD 415)
and for prenatal developmental toxicity (OECD 414; revision of this
test is ongoing at OECD). If separate reproduction and developmental
toxicity tests were conducted using current OECD 415 and 414 protocols,
320 animals would be used. To screen for reproductive and developmental
toxicity and to reduce animal usage in comparison to the separate
test guidelines, EPA recommends use of a combined toxicity protocol
(OECD 421) for the U.S. HPV testing program.

(3) 28-Day repeated dose toxicity. Instead of conducting
a stand-alone 28-day oral toxicity test (OECD 407), the endpoints
covered by that guideline can be combined with the reproduction/developmental
toxicity screen into OECD 422 with no increase in number of animals
over that used in OECD 421.

(4) Mammalian micronucleus. The traditional in vivo micronucleus
test is performed using 2 sexes and a concurrent positive and negative
control. EPA is exploring the idea of using at least the males from
OECD 422 for all but the positive control. Females may need to be
dosed separately.

(5) Overall animal savings. By selecting specific tests,
there could be a significant savings in animals committed to test
in the HPV program. If the traditional acute, reproduction, developmental
and 28-day repeated dose toxicity studies and the in vivo micronucleus
test were separately employed, a total of 440 animals might be used.
By using alternative and combined test protocols, the number of animals
could be reduced to 118, a savings of 322 animals (>70%) per chemical.
Actually, the savings would be greater because most tests employ dose
sighting studies.

Table 1. Potential reductions in animal usage in the U.S. HPV testing
program